Solid-state one-dimensional and two-dimensional photodetectors with picture elements (pixels) based on the charge-coupled-device (CCD) principle are well-known; cf. A. J. P. Theuwissen: “Solid State Imaging with Charge Coupled Devices”, Kluwer Academic Publishers, Dordrecht, 1995. They find use not only in consumer goods such as ordinary cameras, but also in combination with a dedicated light source in special applications such as time-of-flight (TOF) range cameras (cf. EP-1'152'261 A) or in (bio-)chemical sensing (cf. EP-1'085'315 A). For such special applications, the properties of standard CCD pixels may not be sufficient. The pixels perform the tasks of the photo-generation of charges, the separation of said charges and the charge accumulation of said separated charges either in at least one storage site and at least one dump site or in at least two storage sites. For the above-mentioned special applications it is also advantageous to incorporate means of repeated charge accumulation, such as described in U.S. Pat. No. 5,856,667.
An important property of such a CCD pixel is the so-called shutter efficiency. The shutter efficiency is defined as the number of photogenerated charge carriers transported to the desired accumulation site divided by the total number of photogenerated charge carriers. Using state-of-the-art technology, this quantity is in the range between 80% and 95%, which is not sufficient for special applications such as mentioned above, as will be described in the following.